1. Technical Field
The present invention relates to a light source device and a projector.
2. Related Art
In the past, in the projector field, it has been common that the discharge lamp such as a super-high pressure mercury lamp has been used as the light source. However, the discharge lamp of this kind has a problem that the product life is relatively short, a problem that quick lighting is difficult, a problem that the ultraviolet light emitted from the lamp deteriorates the liquid crystal light valve, and so on. Therefore, there is proposed a projector using a light source of a type used instead of the discharge lamp.
For example, in the projector proposed in JP-A-2004-327361 (Document 1), there is used a light source which externally inputs excitation light to a fluorescent body, and then emits the luminescence (fluorescence) thus obtained. Specifically, in Document 1, the light source is proposed as a light source having the total area of the end face of the fluorescent body in the visible light emission direction set to be smaller than the total area of the excitation light emission end face thereof, and capable of emitting intense light from the smaller area than in the case of directly using the light source of the excitation light. According to this structure, there can be realized a bright projector which is high in light efficiency, low in cost, and low in power consumption.
However, in the light source described in Document 1, if too much light is collected in the fluorescent body, the amount of luminescence is reduced due to the following reason.
That is, if the intensity of the excitation light is high, the proportion of the electrons excited in the fluorescence molecule increases and the electrons (the electrons in the ground state) which can be excited decrease, and therefore, a so-called light saturation phenomenon occurs in which emission corresponding to the light intensity of the excitation light becomes unachievable. Thus, it results in that the luminance efficiency (the proportion of the luminance amount of the fluorescent body with respect to the incident light intensity of the excitation light) is degraded. Therefore, it is difficult to obtain a desired light intensity even in the case of using the light source disclosed in Document 1 and increasing the excitation light intensity attempting to obtain the intense light.